When a ballistic round is fired, an explosion takes place just behind the projectile, creating hot gases which expand and force the projectile out of the barrel. In order to insure the greatest power from this explosion, (efficiency), it is necessary to prevent these gases from passing between the internal diameter of the barrel (bore) and the outer diameter of the projectile. This is accomplished by making the tolerances between the bore and projectile very close. However, these close tolerances mean that some physical contact between the projectile and the wall is inevitable as the projectile makes its way through the barrel. This contact creates local stresses in the barrel, which in turn create cracks and fissures along the bore. This physical contact also erodes some of the material thereby enlarging the bore diameter. In addition, the explosion of the powder creates a brisance or shattering effect which places sharp and sudden stresses on the gun barrel. These stresses can create additional fractures, cracks and fissures in low fracture toughness materials which further destroy the close tolerances required for maximum performance. The hot gases which are created during this explosion also add to the deterioration of the bore dimensions. These gases are both erosive and corrosive and have a strong oxidizing effect on the metal alloys presently being used for gun barrel application. These materials do not possess the optimum in corrosion and erosion resistance necessary for a long life. The current state of the art gun barrels are fabricated from stellite lined, chrome-plated steel tubes. Due to the high percentage of the critical elements cobalt and chromium, barrels of this type are becoming increasingly expensive to manufacture.
In light of these limitations a liner made of ceramic materials has been sought for this application because in general, they can provide a greater resistance to erosion and corrosion forms of deterioration. However, ceramics have a low fracture toughness which makes them susceptible to chipping, flaking and cracking from the stresses created during firing and place a serious limitation on their use. Similarly, these ceramics typically have elastic modulii greater than that of the surrounding steel main gun barrel. A typical elastic modulus for steel is 30.times.10.sup.6 psi (206 GPa) while that for high performance ceramics such as silicon carbide, silicon nitride and alumina is approximately 50.times.10.sup.6 psi (345 GPa) or greater. This relatively higher stiffness of the ceramic liner limits the ability of the surrounding steel to provide structural reinforcement and causes high stresses to occur in the ceramic liner during gun barrel firing. A tough, compliant non-metallic tubular liner capable of overcoming the disadvantages present in the prior art could find utility in many areas.